The duration for which a satellite stays in orbit depends on several factors, including its altitude, the atmospheric conditions, and the mission requirements. Here are some key points to consider:
Altitude: Satellites placed in low Earth orbit (LEO), typically around 100-1,200 kilometers (62-746 miles) above the Earth's surface, experience atmospheric drag. This drag gradually reduces their orbital velocity, causing them to lose altitude over time. Consequently, LEO satellites generally have shorter lifespans and need to be replaced or boosted periodically to maintain their orbits. On the other hand, satellites in higher orbits, such as geostationary orbit (GEO) at around 35,786 kilometers (22,236 miles), experience negligible atmospheric drag and can remain in orbit for much longer durations.
Atmospheric Conditions: The density of Earth's atmosphere varies with altitude and solar activity. Satellites encounter atmospheric particles at lower altitudes, which leads to increased drag and accelerates orbital decay. Solar activity, such as variations in the Sun's output, can also affect atmospheric density and satellite lifetimes. Periods of high solar activity can result in increased drag and shorten the lifespan of satellites in low orbits.
Propellant and Design: The amount of propellant carried by a satellite plays a crucial role in determining its orbit and lifespan. Satellites equipped with propulsion systems can perform orbit adjustments to counteract the effects of atmospheric drag and maintain their positions. Additionally, the design of the satellite, including its power systems, communication equipment, and overall construction, influences its operational lifespan.
Mission Objectives: Satellites are launched for specific purposes, such as communication, Earth observation, scientific research, or military applications. The operational lifespan of a satellite is often planned to fulfill its intended mission requirements. Once the satellite has achieved its objectives or if it encounters technical difficulties, it may be decommissioned, deorbited, or placed in a graveyard orbit to make room for newer satellites.
Space Debris: The presence of space debris poses a significant risk to satellites. Collisions with debris can cause irreparable damage or complete destruction of a satellite. To mitigate this risk, satellites are sometimes moved to higher orbits or deorbited at the end of their operational life to reduce the accumulation of debris in heavily used orbital regions.
In summary, the duration a satellite stays in orbit varies depending on altitude, atmospheric conditions, propellant availability, mission objectives, and the presence of space debris. Some satellites can operate for several years or even decades, while others may have shorter lifespans due to their orbit and design constraints.